Reading the docs…
Stopped.
Come back to a board after a while, and Tack shows what happened since your last visit.


When there’s something new, a New button appears in the top bar, and the panel opens by itself once: “Since you were here”, “Away 3 days, since Saturday 12:00”. It has:
Changed shapes on the board get a soft ring: New, Changed, Moved or Closed, with who did it. A ring fades once the shape has been on screen, clear of the panel, for a few seconds after you start looking around (moving the pointer, scrolling or pressing a key), so nothing fades while you’re still reading the digest. The stepper at the bottom of the panel (Previous change, Next change) takes you to each change, the ones you haven’t seen first, and puts it beside the panel rather than behind it. The count on the New button is the changes on the board you haven’t looked at, plus threads with new comments.
Mark all as seen starts the next digest from now, on your other tabs too.
A visit ends when you’ve been away for 15 minutes, so reloading or a quick break doesn’t reset what you haven’t seen. When you’re signed in, your own edits are never in your digest. On your first visit, there’s nothing to show.
If you’re not signed in, your browser remembers when you were last here, for this board.